A Nickel Tripeptide as a Metallodithiolate Ligand Anchor for Resin-Bound Organometallics

The molecular structure of the acetyl CoA synthase enzyme has clarified the role of individual
nickel atoms in the dinickel active site which mediates C−C and C−S coupling reactions. The NiN2S2
portion of the biocatalyst (N2S2 = a cysteine-glycine-cysteine or CGC4- tripeptide ligand) serves as an
S-donor ligand comparable to classical bidentate ligands operative in organometallic chemistry, ligating
the second nickel which is redox and catalytically active. Inspired by this biological catalyst, the synthesis
of NiN2S2 metalloligands, including the solid-phase synthesis of resin-bound Ni(CGC)2-, and sulfur-based
derivatization with W(CO)5 and Rh(CO)2+ have been carried out. Through comparison to analogous well-characterized, solution-phase complexes, Attenuated Total Reflectance FTIR spectroscopy establishes
the presence of unique heterobimetallic complexes, of the form [Ni(CGC)]M(CO)x, both in solution and
immobilized on resin beads. This work provides the initial step toward exploitation of such an evolutionarily
optimized nickel peptide as a solid support anchor for hybrid bioinorganic−organometallic catalysts.